Jeffrey Robert Dawson

Dr. Jeffrey R. Dawson's research centered on the interactions of natural killer cells (NK cells) with endothelial cells. His laboratory and others found significant, noncytotoxic effects of human NK cells on both allogeneic and xenogeneic endothelial cells--inducing an activated endothelial cell phenotype. Most of his studies focused on the activation of monolayers of porcine aortic endothelial cells (PAEC) by human NK cells in vitro. Incubation of CD56+ NK cells on PAEC monolayers for as little as 20 min leads to time-dependent changes in PAEC monolayer morphology. When NK-depleted effector cells were used, no morphological changes were observed in comparison with the same effectors before depletion. Purified human T cells or monocytes had no similar effect on PAEC. There was no detectable NK cell-mediated cytolytic activity during the 1 - 6 h of incubation of PBL with PAEC monolayers. In contrast, cytokine-activated NK cells (e.g., IL-2-activated NK cells) are very cytotoxic to PAEC. These observations suggested that unstimulated NK cells participate in endothelial cell activation leading to acute xenograft rejection, and cytokine-activiated NK cells may cause a cytotoxic, hyperacute rejection. The laboratory also discovered that huuman NK cells induce the expression of procoagulant activity by PAEC and their cell-surface expression of E-selectin.